Rotary compressor



Oct. 6, 1953 T, W, N|CHOLS I 2,654,532

ROTARY COMPRESSOR Filed April 27, 19'48 r f- Attorney Patented Oct. 6, 1953 vThis invention relates to rota-ry compressors f .the ...kind isi/ 13.19.11 @tary Compressori-1S sea-ledwith oilffrom a combined air or gas and oil cgntarlsr- Oil sealed rotary compressors with'the sealing oil supplied under. pressurefrom a combinegrair or gas and oil container have aV tendengr to .130.001 with @il wheesigppedf Q11 restarting, all the Oil-..-gsi be evacuated from the compressor, and this involvesv th' use of-shaft ,torque in"excess.,of'.what d be necessaryand often entailsjthe .use of-,Nahrnotpr of more than necessary power. Y

vTo remedy this 'defecIrI propose to incorporate in a rotary compressor of this type an automatic valve or choke whichwill prevent the passage of sealing oil into the compressor immediately the compressor is stopped.

This automatic prevention of the flow of sealing oil to the compressor from the container may be achieved in various ways one of which will now be described by way of example only with reference to the accompanying drawings in which:

Fig. 1 shows a plan View partly in section of an air compressor tted with an oil choke valve according to the invention and also shows an elevation partly in section of an associated air and oil container.

Fig. 2 shows a modification form of oil choke valve.

A rotary air or gas compressor of the vane type has a rotor I with one or more sliding vanes. The rotor is mounted eccentrically in a stator casing 2 and is arranged to be driven by an electric or other motor by a shaft 3 passing through a stuing box 4 on the casing.

The shaft 5 of the rotor opposite the driving shaft is extended into an extension of the casing 6 and runs in a suitable bush 1.

Inlet and outlet passages 8, 9 for the air or gas are arranged in suitable parts of the casing and are threaded for the attachment of inlet and discharge pipes, non-return valves being tted to the inlet and discharge lines, a lter IIJ for the air inlet may be fitted as shown.

The discharge pipe Il is led to a combined air or gas and oil container I2 and is preferably brought down to Within a short distance of the surface of the oil contained therein.

The air or gas outlet I3 from the container is preferably located near the top so as toV allow .maximum separati@ elf 0,11*..fr0m4the-agrees tainer is led to a sealing oil inlet I5 onthecompressor casing. From the inlet the sealing foil isadmitted tothe-bearings and bore ofwthecompresser through a suitable portorportsdl.

t will be 'apparent that, Wwithr 'apparatus A. as so far described, upon stopping thecomp'ressor sealingoil 4vvill4 be forced' through 1the.,bea`r,ing V'Lof Tthe.- extended y shafts 5 Yunder residual .press .sure-in-the container- I2 and-wille1`fe1irl111'ally.- sub: stantially-#ood the statoncasingcf rthecompres: sor with-oil.

To overcome the disadvantagesv causedeby.. such flooding.. it is -prolcosedrto `insert a yvalve .orchoke irs-thesealing..oilL-spply -line. yto fthe compressor, preferably situated within the compressor casing. This valve may comprise a piston I'I the outer end of which may be arranged to act as a valve, whilst the inner end is adapted to engage a suitable spring I8. The sealing oil is led to the head of the valve through the sealing oil connection I5. A small port I6 connects with the underside of the valve and a chamber I9 at the outer end of the extended rotor shaft 5. This chamber connects with suitable ports (not shown) to lubricate the bearings at either side of the rotor and also passes the oil for sealing the bore of the compressor. A further small port 20 connects the inner end of the piston valve with the delivery port 9 of the compressor.

The action of this piston valve is as follows:

Assume that the compressor is at rest andv that the piston valve has been forced inwards on to its seat. On the apparatus restarting the compressor raises the pressure in the delivery port 9 to the pressure required in the air or gas container I2. This pressure acting on the inner end of the piston and valve with the additional pressure due to the spring I8, being greater than the pressure in the container forces the valve outwards and permits the passage of the oil through the oil delivery port I6 to the chamber I9 from which chamber the sealing oil passes to the bore of the compressor and/or bearings and continues to pass thereto all the time the compressor is running.

On the apparatus being stopped, the-suction valve (not shown) and the delivery surge valve 2I immediately seat themselves. The small amount of gas, at the same pressure as that in the container which is imprisoned in the delivery passage immediately leaks back to the suction side of the bore of the compressor. The

pressure of the gas acting on the inner end of the piston l1 is therefore considerably reduced, so that the pressure on the outer end of the valve which is the same as that in the container, is greatly in excess of the pressure acting on the inner end of the valve causing the valve to be forced inwards, closing the valve and preventing the further passage of the sealing oil to the compressor.

The type of valve used to perform the described operation for preventing the passage of sealing oil to the compressor after it has stopped may be varied as preferred.

For example, the valve may be separate or (as shown in Fig. 2) a ball 22 may be used for the valve having a piston to push it ol its seat on the starting of the apparatus. operation of choking the oil passage is exactly similar to that :already described.

Modifications to the assembly and position of the parts may be arranged to meet requirements as preferred. y

I claim:

1. In combination, an oil sealed rotary vane type compressor, a separate container for the gas discharged by said compressor and for sealing oil, a fluid carrying connection between the discharge of said compressor and said container, a non-return valve in said connection, an oil supply conduit from said container to said compressor, a cylinder in communication at one end with said fluid carrying connection between the compressor discharge and said non-return valve and at the other end to said oil supply conduit, a valve in said oil supply conduit and controlling In this case the oil ow to said compressor, and a piston operative within said cylinder and operatively connected to said valve. whereby movement of said piston under the inuence of pressure generated by the compressor on starting opens said valve to permit a flow of sealing oil and movement of said piston under the influence of residual pressure in said container on stopping said compressor closes said valve to shut off said flow of sealing oil.

2. The combination of claim 1 wherein said piston and said valve are located within the casingof the compressor.

3. The combination of claim 1 including a compression spring in said cylinder and bearing upon said piston to urge it in the direction to open said valve.

4. The combination 'of claim 1 wherein said valve is constituted by a ball co-operating with a seat.

THOMAS WINTER NICHOLS. References cited in the me of this patent UNITED STATES PATENTS Number Name Date 1,686,569 McMillan Oct.v 9, 1928 1,720,310 Wilcox July 9, 1929 1,969,999 Cuthbert Aug. 14, 1934 2,264,616 Buckbee Dec. 2, 1941 2,285,426 Freeman June 9, 1942 FOREIGN PATENTS Number Country Date 559,948 Germany Sept. 8, 1932 

